Adduct ion formation by metal complexes under methane negative chemical ionization conditions

Abstract

Negative chemical ionization mass spectrometry is used as a probe to examine reactions between hydrocarbon radicals and metal complexes in the gas phase. The methane negative chemical ionization mass spectra of 27 complexes of cobalt(II), nickel(I1) and copper(n) in the presence of O,, OzN2 and N4 donor atom sets are characterized by two dominant series of adduct ions of the form [M+C,H,,]-and [M + CnHk+J at m / z values above the molecular ion, [MI-. Insertion of the 'CH radical into the ligand followed by radicallradical recombination and electron capture is proposed as the major mechanism leading to the formation of [M + C,H,]-adduct ions. A second pathway involves ligand substitution by 'C,H,+, radicals concomitant with H' elimination and electron capture. Oxidative addition at the metal followed by ionization is suggested as the principal pathway for the formation of [M + CnHk+J-adduct ions. ~ ~~ ~ ~

Adduct ion formation in the methane-enhanced negative chemical ionization mass spectrometry of 2-(alkylthio)- and 2-alkoxy-s-triazines

“…In contrast to the lack of alkyl anions, alkyl radicals as well as the highly reactive methylidene (CH") and methylene (CH2) species are known to be present at significant concentration in the plasma formed with a hydrocarbon enhancement gas in the mass spectrometer source under high-pressure chemical ionization conditions (2)(3)(4)(5)(6)(7)28). Several studies have demonstrated that for adduct ion formation via a proposed radical/molecule pathway, the abundance of the adduct ion increases as the source temperature and sample pressure decrease.…”

“…The apparently contradictory data from the above series of experiments indicate that further work is needed to deduce the mechanism of adduct ion formation in this series of s-triazine compounds. It may be that the criteria described above to identify radical/molecule reactions (2,7,28) are not valid for all such reactions.…”